Dietary protein and chromium tripicolinate in Suffolk wether lambs: Effects on production characteristics, metabolic and hormonal responses, and immune status

Thirty-two Suffolk wether lambs were fed for 84 d in a 2 x 2 factorial expe riment using two levels of dietary protein (9.0 to 12.1% CP, low protein, L P;or 12.8 to 14.4% CP,high protein, HP) and supplemental Cr (none, C; or 40 0 ppb Cr as chromium tripicolinate, Cr). At 14- to 21-d intervals,lambs wer e weighed, and jugular blood samples were collected. Mean ADG and carcass-w eight (P > .10) did not differ. In lambs fed HP, Cr reduced Liver weight an d increased kidney weight (P < .01). Lambs fed HP had elevated plasma urea N (PUN; P < .01) and albumin (P < .04). During an i.v. epinephrine challeng e on d 43, plasma cortisol declined in lambs fed Cr (Cr x time, P < .03) an d in lambs fed LP (CP x time, P < .001). An i.v. glucose tolerance test con ducted 3 h later showed that supplemental Cr decreased glucose clearance ra te in lambs fed HP (CP x Cr, P < .10) but not in lambs fed LP. On d 62, PUN was increased in lambs fed MP (P < .001) between 0 and 3 h postprandial, a nd there was a Cr x CP interaction (P < .04). Postprandial plasma NEFA. dec lined with Cr vs C (Cr x time, P < .07) and with HP vs LP (CP x time, P < . 10). By d 66, lambs fed Cr had an elevated (P < .03) blood platelet and fib rinogen content. Chromium increased erythrocyte count in lambs fed HP (Cr x CP, P < .08), and isolated peripheral lymphocytes had greater blastogenic response to 4 mu g/mL of phytohemagglutinin (Cr x GP, P < .001). The lympho cyte response to pokeweed mitogen (.2 mu g/mL) was reduced in lambs fed Cr (P < .10). In the present experiment, Cr supplementation had minimal and in consistent effects on production and metabolic criteria of lambs.